1. Field of the Invention
This invention relates to a rotary type pulse switch, and more particularly to a rotary type pulse switch comprising a movable electrode with a rotation center and having a plurality of contacting portions formed in positions of the same radius from the rotation center, and a fixed electrode disposed face to face with the movable electrode and having a plurality of contacted portions arranged in form of stepping stones on the same circumference as a rotation locus of the contacting portions of the movable electrode, wherein rotation information of the movable electrode is detected based on conduction states of the contacting portions and the contacted portions when the movable electrode is rotated.
2. Description of the Related Art
Control input units of mobile telephones, PDAs and game machines, and control input units of home electric appliances, have rotary type pulse switches for detecting the rotating operations thereof. The rotary type pulse switch described in Japanese patent No. 3038286 has a movable electrode with a plurality of contacting portions formed in positions of the same radius from the rotation center, and a fixed electrode disposed face to face with the movable electrode and having a plurality of contacted portions arranged in form of stepping stones on the same circumference as a rotation locus of the contacting portions of the movable electrode. Rotation information such as an amount of rotation, direction of rotation and the like of the movable electrode is detected based on conduction states of the contacting portions and contacted portions when the movable electrode is rotated. The fixed electrode includes a first fixed electrode pattern having one or more of the contacted portions, a second fixed electrode pattern having one or more of the contacted portions, and a common fixed electrode pattern having one contacted portion. Each fixed electrode pattern is arranged in a non-conducting state with respect to the others. While the movable electrode makes one rotation (360° rotation), at least one contacting portion of the movable electrode constantly contacts the common fixed electrode pattern consists of one contacted portion. It is therefore possible to derive the rotation information of the movable electrode from an analysis of timing of switching between a contact state and an insulating state of the movable electrode and first fixed electrode pattern, and timing of switching between a contact state and an insulating state of the movable electrode and second fixed electrode pattern.
With the rotary type pulse switch described in Japanese patent No. 3038286, as noted above, while the movable electrode makes one rotation (360° rotation), the movable electrode constantly contacts the common fixed electrode pattern consisting of one contacted portion. Thus, there is a problem that the movable electrode constantly picks up static electricity during the rotation. When the movable electrode is charged with static electricity, the static electricity will enter varied electrical components electrically connected to the movable electrode and fixed electrode. The electrical components can be damaged by electrostatic discharge.
This invention has been made having regard to the problem noted above, and its object is to provide a rotary type pulse switch constructed such that a movable electrode cannot easily pick up static electricity, while securing a required conduction between the movable electrode and fixed electrode.